SiCl4–ethanol as a trimerization agent for organometallics: convenient syntheses of the symmetrically substituted arenes 1,3,5-C6H3R3 where R = (C5H4)Mn(CO)3 and (C5H4)Fe(C5H5)

Trimerization of acetylferrocene and of (acetylcyclopentadienyl)tricarbonyl-manganese proceeds efficiently in the presence of ethanol and tetrachlorosilane. The resulting 1,3,5-trisubstituted benzenes have been characterized by X-ray crystallography and compared with the structure of (1,3,5-triphenylbenzene)tris(tricarbonylchromium). The efficacy of EtOH–SiCl 4 as a combined reagent for the trimerization of polycyclic ketones is also discussed. Finally, the synthesis and structure of [CpMn(CO) 2 ] 2 (µ-C=CHPr), derived from the reaction of cymantrene with butyllithium and phenylacetyl chloride at room temperature, is described.Key words: ketone, condensation, cyclization, organometallics, arenes.